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4-1 Samples and Surveys Pre-Algebra Problem of the Day Problem of the Day Lesson Presentation Lesson Presentation

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Pre-Algebra 4-1 Samples and Surveys Problem of the Day Mr. Gray’s 29 students will be sitting in the gym to watch a play. There are two rows of five chairs, three rows of four chairs, and four rows of two chairs. Is there enough room for all the students to sit? yes

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A fitness magazine printed a readers’ survey. Statements 1, 2, and 3 are interpretations. Which do you think the magazine would use? 1. The average American exercises 3 time a week. 2. The average reader of this magazine exercises 3 time a week. 3. The average reader who responded to the survey exercises 3 time a week.

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A fitness magazine printed a readers’ survey. Statements 1, 2, and 3 are interpretations. Which do you think the magazine would use? THIS IS IMPORTANT- WRITE THIS DOWN! The population is the entire group being studied. The sample is the part of the population being surveyed. 1. The average American exercises 3 time a week. 2. The average reader of this magazine exercises 3 time a week. 3. The average reader who responded to the survey exercises 3 time a week.

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The population is the entire group being studied. The sample is the part of the population being surveyed. For statement 1, the population is all Americans and the sample is readers of the fitness magazine who chose to respond. This is a biased sample because it is not a good representation of the population 1. The average American exercises 3 time a week. 2. The average reader of this magazine exercises 3 time a week. 3. The average reader who responded to the survey exercises 3 time a week.

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Additional Example 1A: Identifying Biased Samples Identify the population and the sample. Give a reason why the sample could be biased. A. A record store manager asks customers who make a purchase how many hours of music they listen to each day. PopulationSamplePossible Bias Music store customers Customers who make a purchase Customers who make a purchase might be more interested in music than others in the store

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Pre-Algebra 4-1 Samples and Surveys Try This: Example 1A A. The first 5 people leaving a movie theater at a sneak preview were asked how they liked the movie. People that went to the movie The first five people that left People that really enjoy a movie are less likely to be of the first ones to leave. PopulationSamplePossible Bias Identify the population and the sample. Give a reason why the sample could be biased.

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Additional Example 1B: Identifying Biased Samples B. An eighth-grade student council member polls classmates about a new school mascot. Identify the population and the sample. Give a reason why the sample could be biased. PopulationSamplePossible Bias Students in the school Classmates She polls more eighth-graders than students in other grades.

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Pre-Algebra 4-1 Samples and Surveys B. Eighth-grade students with a 3.0 GPA or higher were polled to determine how long students study each day. Eighth grade students Students with 3.0 or higher GPA Students with lower grades are less likely to study as long. Try This: Example 1B Identify the population and the sample. Give a reason why the sample could be biased. PopulationSamplePossible Bias

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Additional Example 1C: Identifying Biased Samples C. A television reporter asks people on downtown streets if they support a new city subway system. Identify the population and the sample. Give a reason why the sample could be biased. PopulationSamplePossible Bias People in the city People on downtown streets People working downtown might show more support than people who work elsewhere.

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Pre-Algebra 4-1 Samples and Surveys C. People attending a baseball game were asked if they support the construction of a new stadium in the city. City residents People attending a game People that attend a baseball game are more likely to support the construction of a new stadium. Try This: Example 1C Identify the population and the sample. Give a reason why the sample could be biased. PopulationSamplePossible Bias

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Pre-Algebra 4-1 Samples and Surveys Lesson Quiz: Part 1 ONLY Identify the population and sample. Give a reason why the sample could be biased. 1.A high school principal asks the first three people who leave the school play whether they liked it. People that went to the play The first 3 people leaving People that enjoy a play may not leave as early as someone who didn’t. PopulationSamplePossible Bias

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Pre-Algebra 4-1 Samples and Surveys Additional Example 2A: Identifying Sampling Methods Identify the sampling method used. A. In a county survey, Democratic Party members whose names begin with the letter D are chosen. systematic The rule is to survey members whose names begin with D.

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Pre-Algebra 4-1 Samples and Surveys C. A high school randomly chooses three classes from each grade and then draws three random names from each class to poll about lunch menus. stratified The three classes are the random subgroups. Names are chosen randomly from within the classes. Additional Example 2C: Identifying Sampling Methods Identify the sampling method used.

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Pre-Algebra 4-1 Samples and Surveys Try This: Example 2A Identify the sampling method used. A. In a county survey, families with 3 or more children are chosen. systematic The rule is to survey families with 3 or more children.

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Pre-Algebra 4-1 Samples and Surveys C. At a basketball game 5 sections are chosen at random and 20 people from each section are randomly polled. stratified The five sections are the random subgroups. 20 people are chosen randomly from within the sections. Try This: Example 2C Identify the sampling method used.

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Pre-Algebra 4-1 Samples and Surveys Lesson Quiz: Part 2 Identify the sampling method used. 2. At a baseball game, 10 sections are chosen at random and 10 random people from each section are polled. 3. A telemarketer calls the people that have a last name beginning with H. systematic stratified